Automatic drip coffee maker

ABSTRACT

Conventional automatic drip coffee makers require about one minute of manual involvement to commence a brewing cycle. 
     The automatic drip coffee maker herein disclosed makes a full decanter of coffee within 11/2-2 minutes following the one minute manual involvement. 
     The automatic drip coffee maker of the present invention uses preheated water but only the amount required for a decanter of coffee (1/2 gallon) making it unnecessary to employ a large reservoir. The concept, in a preferred embodiment, is to commence the brewing cycle by an almost instantaneous dump of the preheated water to a transfer tank which, in turn, meters heated water to the grounds at such a rate as to insure almost immediate contact between all the coffee grounds and all the hot water. The dump time for preheated water from the preheated reservoir to the transfer tank is less than the time required to fill a receptacle with cold water. Thus by the time cold water addition may be made to the automatic drip coffee maker, the preheat tank is empty and coffee is in the process of being brewed.

BACKGROUND OF THE INVENTION

The invention relates to automatic drip coffee makers.

A drip coffee maker is one in which coffee brew is obtained by a singlepass of hot water through a quantity of coffee grounds. The hot waterflow to and through the coffee grounds may be intermittent or continuousbut the entire quantity of water flows through the grounds only once asopposed to a recirculating flow characteristic of percolator type coffeemakers.

In the case of a typical, non-automatic drip coffee maker; coffeegrounds are placed in the coffee maker, and water is heated in aseparate container, such as a tea kettle, from which hot water issubsequently poured into the drip coffee maker. Manual involvement isalways required at two time spaced intervals (to start the heating ofthe water and pouring of the same into the coffee maker approximatelyseven minutes later); and, in most cases, there is a third requiredinvolvement which is the placement of the coffee maker on a "keep warm"element shortly after the coffee is brewed.

In contrast, an automatic drip coffee maker is a self contained unitwhich heats water, flows the same across coffee grounds and keeps thebrewed coffee hot. The only manual involvement is that which takes placeat one point in time, i.e. commencing a brewing cycle by adding coffeegrounds and water to the maker and energizing the same. The manual timerequirement to commence a brewing cycle is about one minute. Completionof the brewing cycle may take from 21/2 to 15 minutes depending on thetype automatic drip coffee maker employed.

Automatic drip coffee makers may, on the basis of their heated waterflow systems, be categorized as being of the intermittent pumping, weiroverflow or preheated displacement type.

INTERMITTENT PUMPING TYPE

In this type coffee maker, small quantities of cold water aresuccessively withdrawn from a reservoir, heated and pumped to a filterbasket containing coffee grounds. The outlet coffee flow from the filterbasket into a serving decanter is, similarly, intermittent. Coffee brewtime for a conventionally sized, half gallon decanter of coffee willvary from 8 to 15 minutes depending upon the heater wattage employedwhich, typically, falls within a range of 750-1500 watts.

An inherent characteristic of the intermittent pumping type coffee makeris that it may be relatively small since the water reservoir thereforneed not hold more than approximately one half gallon. Furthermore,because a pump is employed, the reservoir need not overlie the filterbasket for gravity flow thus allowing the positionment of the same inthe vertical standard, below the filter basket, to ensure a low centerof gravity. This permits a wide variety of aesthetic design approacheswithin a stable, slim appliance profile. The component parts of apumping drip coffee maker are relatively inexpensive and this, combinedwith the relatively small amount of plastic or other housing materialrequired for the slim profile appliance, allows this type coffee makerto be sold at a price competetive with other, non-drip type coffeemakers, such as electric percolators.

The advantages of the pumping type drip coffee maker are, then; smallsize, low cost and a low center of gravity permitting a wide variety ofdesign approaches.

The primary disadvantage in this type coffee maker is the requiredbrewing time. A second disadvantage is the quality of the coffee brewedin the intermittent fashion described above.

WEIR OVERFLOW TYPE

In this type drip coffee maker, cold water is poured into a panoverlying a tank having a rod heater element and a weir therein. Thecold water flows continuously, by gravity, into the underlying tankwhere it is heated by the rod heater before it overflows the weir fromwhich the heated water flows by gravity into an underlying filterbasket.

As compared with a pumping type coffee maker, the weir overflow type hasone advantage and several disadvantages.

The advantage is speed. Brew time is approximately 5 minutes using amaximum wattage heater.

The disadvantages are:

(1) The coffee quality is poor. Upon start-up, the initial cold waterflow into the heating tank is such that the initial water flowing acrossthe weir has not been brought up to proper brewing temperature. Themajority of coffee flavor is obtained at initial brewing contact andsince the initial contact is by water below the correct brewingtemperature the coffee quality is below that which is obtainable whenall the water passing through the coffee grounds is at the correcttemperature.

(2) The design appearance is, necessarily, cumbersome and ungainly.Since the inpour pan must have a one half gallon capacity and theunderlying heating tank must have at least half the pan capacity plusthe heater element and electrical controls; and since all of these mustoverlie the filter basket for successive gravity flows from the pan totank and tank to basket it is apparent that the unit will not onlyappear top heavy but will, in fact, have a high center of gravity whichmust be compensated for in some fashion. Usually, this compensationtakes the form of a large base and a large vertical standard to supportthe tank and pan.

(3) The appliance life time is short. The use of a maximum wattageheater is critical to this operational mode and, as with all appliances,the operational life of a heater element varies inversely with thewattage.

PREHEATED DISPLACEMENT TYPE

In this type drip coffee maker, a large quantity of water is preheatedand thermostatically maintained at correct brewing temperature. To makecoffee, a quantity of cold water is introduced, via a holding pan andinlet tube, to the bottom of the preheated water whereupon an equalquantity of the preheated water is displaced from the top thereof, viaan outlet tube, to flow to an underlying filter basket.

The quantity of preheated water is necessarily large as compared withthe quantity of cold water to be added to the bottom of the preheatedwater to insure that the displaced, preheated water is not cooled by thecold water addition. Typically, the ratio of preheated water to coldwater addition is 3:1. The capacity of the preheat water tank would thusbe 11/2 gallons while that of the holding pan is 1/2 gallon. The totalrequired water capacity that must be accomodated within the appliancehousing is, then, 2 gallons.

This type coffee maker, when new, has two distinct advantages over otherautomatic drip coffee makers; speed and brew quality. An unusually largefilter basket is typically employed and the hot water is introduced atsuch a rate that the coffee grounds are literally floated in a largequantity of hot water. The inpour rate to the filter basket and theoutflow rate therefrom (as metered by the size of the inflow and outflowopenings) is such as to insure that the hot water/coffee suspension isjust short of overflowing the filter basket until all the hot water hasbeen introduced. The key to the superior coffee quality is that theinitial brewing contact is between a large body of water at correctbrewing temperature and all of the coffee grounds. A through flow timeof approximately 21/2 minutes is obtainable with this type coffee maker.

In contrast, however, both coffee quality and brew time deteriorate withusage. Because it is necessary to meter the hot water outflow to thefilter basket to prevent overflowing the same the outflow tubing must befairly small, as on the order of 1/4" OD. The cold water inflow tubewhich introduces cold water to the bottom of the preheated water issimilarly sized. Both of these tubes are quite long and constantlyheated. Mineral deposits thus quickly build up resulting in a lesserinflow rate to the filter basket with a subsequent increase in brew time(up to 41/2 minutes is typical) and a slight lessening of coffee qualityas the coffee ground suspension action, discussed above, is decreased.Of greater concern to brew quality is the break up of these mineraldeposits and their subsequent delivery to the serving decanter as isreadily apparent from visual inspection of a serving decanter that hasbeen in use for some time. Althought it is possible to ream these tubeswith a long "snake" and again achieve the faster brewing time the offsetis that the reamed mineral particles fall into the preheat tank. Of moreimportance to brew quality is the fact that "old" water is used to makethe coffee. If several gallons of coffee are made daily, this is oflittle concern but if only one or two half gallon containers are madedaily, the user will be making coffee with water that has beenconstantly heated for one or two days.

Notwithstanding the foregoing, brew times are shorter and brew qualityis superior to other automatic drip coffee makers.

The primary disadvantages are cost, size and initial brewing time from acold start before the water is preheated. The size, alone, of theappliance profile necessary to have a 2 gallon capacity along with theelectrical controls creates a substantial difference in cost as comparedwith other coffee makers. It is also necessary that the housing be quitetall since the concept of operation requires a "stratification" of coldwater introduced to the bottom of the preheated water to displace thesame from the upper volume thereof without mixing. Also contributing togreater cost is insulation for the preheat tank, the necessarily heavierrod heater to preheat and maintain 11/2 gallons of water as comparedwith the 1/2 gallon for other coffee makers and the requiredthermostatic controls. On initial start up, such as when the unit isfirst turned on in the morning, the first coffee cannot be made untilthe 11/2 gallons of water is preheated which takes about 35 minutes.

Because of its necessary bulk and height, this type coffee makerrequires a large amount of counter space and does not lend itself to theaesthetic designs possible with smaller coffee makers.

COMPARISON

From the foregoing, it will be seen that the attributes of the variousautomatic drip coffee makers (ADCs) break down as follows:

    ______________________________________                                        ADC                     BREW   BREW    AES-                                   TYPE   SIZE     COST    TIME   QUALITY THETICS                                ______________________________________                                        inter- small    low     slow   fair    good                                   mittent                                                                       pumping                                                                       weir   medium   low     medium poor    poor                                   overflow                                                                      pre-   large    high    fast   good    poor                                   heated                                                                        displace-                                                                     ment                                                                          ______________________________________                                    

It is the purpose of the present invention to combine the more desirableof the above tabulated attributes in a single, automatic drip coffeemaker.

More specifically, the automatic drip coffee maker herein disclosed isof the same small size and low cost as the intermittent pumping type andhas a very fast brew time (21/2 minutes per half gallon)(11/2-2 minutes"waiting" time following manual involvement) to deliver an excellentbrew quality.

SUMMARY OF THE INVENTION

As stated above, an automatic drip coffee maker (ADC) is one in whichmanual involvement takes place at only one point in time. That is thetime period during which coffee grounds and cold water are added to theADC. In most ADCs an electrical circuit is energized during this"start-up" time period although in the preheated displacement type, theheater circuits are continuously energized. Thus, a common factor of allADCs is the addition of coffee grounds and water with the commencementof the brew cycle being initiated either by the energization of aheating circuit or as a function of having added cold water as in thedisplacement type. In any event, the commencement of the brewing cyclecannot take place before the cold water addition. Conversely, it is animportant distinction in a preferred mode of operation of the presentinvention that the brew cycle be initiated prior to the addition of coldwater.

The manual involvement referred to above normally requires about oneminute with 20-30 seconds of that time being required to fill areceptacle with the cold water to be added to the ADC. In a preferredembodiment of the present invention it is the operation of the ADCwithin that 20-30 second interval required to fill a receptacle withcold water that is important.

Briefly, in accordance with a preferred mode of operation; coffeegrounds are added, the brew cycle is next started and, thereafter, coldwater is added as opposed to conventional ADCs in which the brew cycleis not started before cold water is added. In either event, the requiredtime period of manual involvement (about one minute) is the same.

The ADC of the present invention uses preheated water but only theamount required for a decanter of coffee (1/2 gallon) making itunnecessary to employ a large reservoir. The concept, in a preferredembodiment, is to commence the brewing cycle by an almost instantaneousdump of the preheated water to a transfer tank which, in turn, metersheated water to the grounds at such a rate as to insure almost immediatecontact between all the coffee grounds and all the hot water. The dumptime for preheated water from the preheat tank to the transfer tank isless than the time required to fill a receptacle with cold water whenthe user is necessarily away from the ADC. Thus by the time cold wateraddition may be made to the ADC, the preheat tank is empty and coffee isin the process of being brewed.

In a preferred embodiment, the cold water addition is made to a coldwater reservoir in the vertical standard supporting the preheatreservoir from whence the cold water is heated and intermittently pumpedto the preheat reservoir where it is kept preheated awaiting the nextbrew cycle.

Although the primary purposes of the present invention are met by addingthe cold water directly to the preheat reservoir rather than pumping thesame thereto, there are economic advantages in using the standard,relatively cheap, pumping units that are readily available and requireno connections through the wall of the preheat reservoir as would be thecase if a sufficient wattage heater were positioned therein to bringcold water up to correct brewing temperature. Once the elevatedtemperature is achieved by the pumping unit; a small, economical ropeheater simply attached to the under surface of the preheat reservoir issufficient to maintain the elevated temperature. Another importantreason for cold water addition to a separate cold water reservoir is tofacilitate the making of less than a full decanter of coffee and toinsure that if less than a full decanter of coffee is made on successiveoccassions there will be no stale, or old, water build-up.

Another reason for cold water addition to a separate reservoir has to dowith the required fast dump time from the preheat reservoir. If all thepreheated water may be dumped (the preheat tank completely drained) eachtime coffee is made, then the dump valve may be so positioned (at alevel beneath the reservoir base) as to provide maximum head pressurefor the dump. It is an important aspect of the invention that thistransfer of preheated water is by way of gravity flow through a dumpvalve as opposed to a syphon flow characteristic of displacement typeADCs.

The dump valve construction, position, and mode of operation is animportant facet of the invention, primarily from the standpoint of costand secondarily as a function of the fast flow rate that may be had. Theformer for obvious reasons and the latter to insure a sufficiently fastintroduction of hot water to the coffee grounds to substantially,instantaneously expose all the coffee grounds to all of the water. Theimmediate, or almost instantaneous, exposure is the key to making thebest possible coffee from the coffee grounds and water available.

The dump valve is nothing but an open ended bent tube, sealed andjournalled by an O ring, that is rotatable through 90°.

In those use conditions where only one decanter of coffee will be madein a day, the ADC herein disclosed is readily convertible to anintermittent pumping type coffee maker.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the new automatic drip coffee maker(ADC) with the cold water inpour door shown partly raised to illustratedetails;

FIGS. 2A, 2B and 2C are schematic illustrations to show the water flowpath within the ADC;

FIG. 3 is a vertical section, with parts in elevation, taken along line3--3 of FIG. 1 but with the inpour door shown closed;

FIG. 4 is a vertical section taken along line 4--4 of FIG. 3;

FIG. 5 is a top plan view with the upper cover removed; and

FIG. 6 is a sectional view taken along line 6--6 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 is illustrated an automatic drip coffee maker 10 whose base 12supports an upper housing 14 through the intermediary of a verticalhousing or standard 16. A cold water reservoir 18 is contained withinvertical housing 16 while housing 14 is divided into an upper, preheattank 20 and a lower transfer tank 22.

Dump valves 24 and 26, best shown in FIGS. 4 and 5, comprise open endedtubes 28, 30 whose opposite ends are offset 180° and 90°, respectively.The O ring mounting and sealing of both dump valves relative to preheattank 20 is identical and is best illustrated in the case of valve 24shown in FIG. 4. Tube 28 is fitted with a collar 32 which has motionclearance within a journal sleeve 34 extending through wall 36 ofpreheat tank 20. Journal sleeve 34 is welded or otherwise secured inwater tight fashion to wall 36 and is so sized relative to the bentoutlet end 38 of tube 28 to permit the indicated assembly. Collar 32 andsleeve 34 are formed with mating, semicircular recesses for the receiptof O ring 40.

Operating rods 42, 44 are secured, as by welding or the like, to thebent outlet ends of tubes 28, 30 along the respective axes of rotationof the same within their respective journal sleeves. The other ends ofthe rods extend through a sidewall of housing 14 and are fitted withoperating knobs 46, 48. Inasmuch as the location at which operating rods42, 44 exit housing 14 is never submerged, only grommet seals need beemployed between the rods and housing. The bent inlet ends 50, 52 of thedump valves are of such length as to approach the horizontal plane oftop 54 of housing 14 when they are positioned in the "off" or non-dumppositions illustrated in FIGS. 3 and 4. Both valves are rotatablethrough 90° to the full dump positions illustrated in FIG. 6. As bestillustrated in FIG. 5, a well 56 is formed in preheat tank 20 into whichthe inlet end 52 of dump valve 26 extends when rotated to the full dumpposition of FIG. 6.

Dump valve 24 transfers water from preheat tank 20 to cold waterreservoir 18. Dump valve 26 transfers water form preheat tank 20 totransfer tank 22. The bottom wall 58 of transfer tank 22 is formed witha central concave portion 60 through which exit, or metering holes, 62extend.

A cold water inpour port 64 formed in housing top 54 is normally closedby a hinged door 66. Cam operators 68, 70 are secured to theundersurface of door 66 and their hooked lower ends 72, 74 coact withcam arms 76, 78 integral with tubes 28, 30. The purpose of the coactingcam operators and arms is to automatically return dump valves 24, 26from a dump position to a closed or non-dump position as a function ofdoor opening movement. This insures that cold water cannot be added tothe coffee maker unless the dump valves are in a non-dump position.

The method of heating and transferring water from cold water reservoir18 to preheat tank 20 is entirely conventional and may employ any of thepresently known intermittent pumping systems. More specifically, coldwater from reservoir 18 flows by gravity via reservoir outlet tube 80and past check valve 82 into heater tube 84. The water volume that canbe accommodated in tube 84 is heated to boiling by rod heater 86 andexpelled via standpipe 88, flexible tube 90 and diffuser head 92 to exitin preheat tank 20. Following this volume expulsion from heater tube 84,additional cold water inflows from reservoir 18 and the cycle isrepeated until all the water from reservoir 18 has been heated andpumped to preheat tank 20 following which time a conventionalthermostat, not shown, breaks the power circuit to rod heater 86.Diffuser head 92 is of conventional construction and, in a conventionalintermittent pumping ADC, comprises the hot water exit immediately intothe filter basket. The diffuser head 92 as employed herein is mounted ona post 94 secured, by welding or the like, to the floor of preheat tank20.

The electrical connections 96 to the rod heater are entirelyconventional as are the connections to a conventional rope heater 98contained in a metal housing 100 butted against the undersurface ofdecanter warming plate 102.

An identical rope heater and housing 104 are butted against theundersurface of preheat tank 20 and moisture sealed with respectthereto. Electrical connections 106 to housing 104 extend throughreservoir 18 via standpipe 108.

The rope heaters contained in housings 100 and 104 may be activated bythe same manual switch 110 although separate switches, not shown, arepreferred for these two rope heaters. Input power to rod heater 86 ismanually controlled by switch 112.

In the particular embodiment shown, there are twelve, 3/32 ID meteringholes 62 providing a gravity flow path from transfer tank 22 to theunderlying filter basket 114 which is conventionally, removablysupported thereunder by coacting slide supports 116, 118.

Assuming a fill volume of sixty-four ounces in preheat tank 20, a fullmeasure of coffee grounds in filter basket 114, a 3/16" ID exit flowport 119 from the filter basket and a dump valve tube ID of 1/2"; thenupon rotating dump valve 26 to the full dump position of FIG. 6 theoutflow from tank 20 to tank 22 is at such a rate as to dump all thewater from tank 20, down to the upper level of well 56, in less timethan is required to fill a decanter with cold water. The simultaneouslyoutflowing rate of hot water from tank 22 to filter basket 114considered in conjunction with the coffee outflow rate from filterbasket exit port 119 is such that:

(1) The water/coffee suspension in filter basket 114 reaches a maximumvolume just short of overflowing the filter basket; and

(2) The maximum volume resident in transfer tank 22 at any time is notmore than approximately one-half the original volume in preheat tank 20and, as such, does not normally rise to the level where dump valveoperating rod 44 exits the preheat tank.

For reasons previously explained, it is desirable to dump all of the hotwater from preheat tank 20 on each brewing cycle. In order to make tenfive-ounce cups it is desirable to use approximately sixty ounces ofwater to take into account water that is retained with the coffeegrounds. In the present invention; also taken into account isevaporation from preheat tank 20 (about two ounces over 3-4 hours,depending upon how well the cover and dump valves are sealed) andresidual volume in well 56 (about two ounces). Consequently, about 64ounces of water is normally put in reservoir 18 as may be viewed bysightglass 120. If a full decanter of coffee is to be made, nomanipulation of dump valve 24 is required because it is normallyimmaterial whether the full decanter contains two or three ounces moreor less than anticipated. If, however, less than a full decanter is tobe made, dump valve 24 is rotated by knob 46 to the desired number ofcups to be made as viewed on scale 122. Assuming, for simplicity ofdiscussion, that one wishes to make four cups of coffee: knob 46 wouldthen be rotated clockwise to the four-cup indication on scale 122 whichwould lower the inlet end 50 of dump valve 24 below the water surfacethat amount necessary to drain six cups of water from preheat tank 20back to reservoir 18. Thereafter, when knob 48 is rotated to the fulldump position (90° clockwise from the position of FIG. 1), the waterneeded for four cups of coffee would be dumped to the transfer tank formaking the coffee and, subsequently, less cold water addition would berequired to bring reservoir 18 back up to the fill mark.

Assuming less than a full decanter of coffee to have been made asdiscussed above, both of the dump valves will have been rotatedclockwise from the dump valve closed positions of FIG. 3. Thus, cam arms76 and 78 will have been moved downwardly from the position of FIG. 3(cam arm 78 will have moved to the position of FIG. 6) to overlie thearcuate path of movement traversed by hooked ends 72, 74 of camoperators 68, 70 when door 66 is moved upwardly about hinge 124.

In operation, on initial cold start-up; door 66 is opened and cold wateris poured directly into reservoir 18 as schematically illustrated inFIG. 2A. If either of the dump valves 24, 26 had been rotated clockwisefrom the closed, FIG. 1 position, the hooked ends of cam operators 68,70 engage the undersurfaces of cam arms 76, 78 and rotate the dumpvalves counter clockwise to the positions shown in FIGS. 1, 2B, 3, 4 and5 as a function of the door opening movement. Door 66 is closed.Switches 110 and 112 are energized and water from reservoir 18 isintermittently pumped to preheat tank 20 as schematically illustrated inFIG. 2B. Since both dump valves are above the preheat water level thewater is retained in tank 20 where it is kept hot by the rope heater inhousing 104. Rod heater 86 cuts off automatically when reservoir 18 isempty even though switch 112 remains energized. The operation of the ADCfrom the time of initial cold startup until the condition of FIG. 2B isobtained is somewhat less than ten minutes. Ignoring for the moment thecold water start-up procedure just described; for all subsequent uses ofthe ADC; its initial condition is as schematically illustrated in FIG.2B with the preheat tank 20 filled and both dump valves closed as inFIGS. 2B and 3.

Assuming it is desired to make less than a full decanter of coffee:

(1) Dump valve 24 is rotated clockwise to the desired setting on scale122 to dump that water in excess of the amount required back toreservoir 18 as illustrated by the position of dump valve 24 in FIG. 2C.

(2) Coffee grounds are then added to filter basket 114.

(3) A decanter is placed on warming plate 102.

(4) Dump valve 26 is rotated clockwise 90° to the full dump positionschematically illustrated in FIG. 2C to commence the brew cycle as thepreheat tank is dumped to the transfer tank which, in turn, meters hotwater at a fast rate to the filter basket.

(5) A second decanter is filled with cold water while the preheat tankempties.

(6) Door 66 is opened which automatically restores both dump valves tothe closed position of FIGS. 2B and 3.

(7) Cold water is added to reservoir 18 up to the fill line as will beseen in sightglass 120.

(8) Door 66 is closed and the manual involvement is complete.

(9) Over the next few minutes, the newly added water is pumped to thepreheat tank so that the ADC is again ready to make coffee.

The time requirement for the above mentioned manual involvement is thesame as for any ADC (approximately one-minute) but the difference isthat the decanter will be half-filled with coffee by the time door 66 isclosed. Thus the "waiting" time for coffee is about 11/2-2 minutes asopposed to the next fastest ADC which is 21/2-3 minutes.

In most cases, the user will want to make a full decanter of coffee inwhich event dump valve 24 is not rotated, i.e., step 1, above, iseliminated.

At the end of the day, the switches are deenergized, an empty decanteris placed on plate 102 and dump valve 26 is rotated to the full dumpposition to drain all the water from the coffee maker.

An important feature of the disclosed ADC is its convertability from apreheat type ADC to a conventional intermittent pumping type ADC. Thisis desirable if only one decanter of coffee is to be made in a day. Thusif a person only drinks coffee for breakfast there would be no need tokeep a volume of preheated water for the remainder of the day.

To use the ADC herein disclosed in the manner of a conventional ADC, itis only necessary to rotate dump valve 26 to the full dump positionbefore energizing switch, 112. The water will then be intermittentlypumped to tank 20 from which it will intermittently flow by gravitythrough tube 30 to transfer tank 22 and through holes 62 to the filterbasket. When using the coffee maker in this fashion, switch 110 shouldbe energized before the coffee grounds and cold water are added to allowadditional time for the rope heater in housing 104 to preheat the tanksthrough which the intermittently pumped water will flow.

I claim:
 1. In an automatic drip coffee maker having housing meanssupporting a filter basket in upper spaced relation to a decanterwarming plate, the improvement comprising; said housing means includingpreheat and transfer tanks; means including a cold water inpour port forintroducing water from outside said coffee maker to said preheat tank;heating means within said coffee maker for heating said water andmaintaining the same at an elevated temperature; flow control means forselectively retaining water in said preheat tank and dumping water fromsaid preheat tank to said transfer tank; and metering means for meteringwater from said transfer tank to said filter basket.
 2. The coffee makerof claim 1 wherein said housing means includes a cold water reservoir;and said inpour port opening into said cold water reservoir.
 3. Thecoffee maker of claim 2 wherein said means for introducing water fromoutside said coffee maker to said preheat tank further includesintermittent pumping means comprising said heating means and conduitmeans for transferring said water from said cold water reservoir to saidpreheat tank.
 4. The coffee maker of claim 3 wherein said flow controlmeans comprise an open ended tube having a central portion thereofextending through a wall of said preheat tank and an inlet end portion,angularly related to said central portion, opening into said preheattank and the opposite, outlet end portion opening into said transfertank; and means mounting said inlet end of said tube for selectivemovement thereof between first and second positions respectivelyadjacent the upper and lower levels of said preheat tank whereby on/offflow control may be effected by selective movement of said inlet end. 5.The coffee maker of claim 1 wherein said flow control means comprise anopen ended tube extending through a wall of said preheat tank and havinginlet and outlet ends opening into said preheat tank and said transfertank, respectively; and means mounting said tube for selective movementof said inlet end between a first position with the open inlet endthereof adjacent the top of said preheat tank to extend above a fillwater level therein and a second position with the open inlet endthereof adjacent the bottom of said preheat tank whereby on/off flowcontrol is effected by selective movement of said inlet end between saidfirst and second positions.
 6. A coffee maker as in claim 5 in whichsaid metering means comprise a plurality of holes in the floor of saidtransfer tank; and the cross section of said open ended tube comprisingsaid flow control means being large as compared with the aggregate crosssection of said holes comprising said metering means whereby water insaid preheat tank may be dumped to said transfer tank at a faster flowrate than water is metered to said filter basket.
 7. A coffee maker asin claim 5 in which said tube mounting means comprises an O ringsealingly interposed between said wall of said preheat tank and acentral portion of said tube; and said inlet end of said tube beingangularly related to said central portion thereof.
 8. A coffee maker asin claim 5 including second flow control means for dumping water fromsaid preheat tank back to said cold water reservoir.
 9. The coffee makerof claim 1 including a door for opening and closing said cold waterinpour port; means connected to said flow control means for moving thesame to a first position for dumping water in said preheat tank to saidtransfer tank; and coacting means respectively connected to said doorand to said flow control means for moving said flow control means to asecond position for retaining water in said preheat tank as a functionof opening movement of said door.